Field of the Invention
The present invention relates to a fixing apparatus used in an image forming apparatus, for example, a copier and a laser beam printer (LBP) employing an image forming process, such as an electrophotographic method and an electrostatic recording method.
Description of the Related Art
A fixing apparatus with a film having a tubular shape is known as a fixing apparatus which is disposed in an electrophotographic image forming apparatus. Such a fixing apparatus includes a film having a tubular shape, a heater that contacts an inner surface of the film, and a pressing member that forms a nip portion with the heater via the film. Generally, in the nip portion, the fixing apparatus applies heat to a toner image while conveying a recording medium bearing the toner image.
As for such a fixing apparatus with the film having a small heat capacity, temperature of a region in which a recording medium does not pass tends to excessively rise although warm-up time is short. That is, a sheet non-passing area temperature rise is liable to occur. Japanese Patent Application Laid-Open No. 11-84919 discusses a configuration in which a heat conduction member is arranged between a heater and a heater support member. Such a configuration facilitates movement of heat inside a surface of the heater so that a temperature distribution of the heater in a longitudinal direction becomes uniform.
However, in a fixing apparatus including a heat conduction member that contacts a heater as discussed in Japanese Patent Application Laid-Open No. 11-84919, the heater may move in a longitudinal direction due to longitudinal thermal expansion of the heat conduction member. In such a case, the heater is displaced from a reference position. The displacement of the heater causes displacement of a heating region of a recording medium by a film. This may deteriorate fixability of a toner image.